Existing integrated circuit (IC) manufacturing lines typically include large clean rooms and some manufacturing tools in the clean rooms, while other tools, such as metrologies and wafer transferring/transporting/exchanging paths, are within a relatively open environment. When exposed to the open environment, wafers are vulnerable to the attacks of adverse substances such as moisture, oxygen, and various airborne molecular contaminants (AMC) sources, which include etching byproduct solvents, perfumes, storage materials, chamber residual gases, etc. An example of the AMCs is dimethyl sulfide (DMS), which is a chemical commonly used in the semiconductor manufacturing processes.
As the semiconductor processes precede into the nanometer domain, the negative effects of AMCs on IC manufacturing become increasingly more severe. In some critical stages, AMCs have posted serious problems impacting either device performance or metrology accuracy. For example, in the formation of copper features in metallization layers, due to the very small size of copper features, the reaction caused by oxygen, moisture, and the AMC sources causes the increase in RC delay, and even the reduction in production yield. Low-k dielectric materials for forming metallization layers are also vulnerable to the attack of chemicals such as acids.
Existing IC manufacturing lines do not provide effective means for protecting wafers from the above-discussed problems. Some processing and transporting steps are not even protected by clean rooms. Further, even if some process steps are performed in clean rooms, the wafers are still exposed to some detrimental chemicals. For example, DMS molecules are small, and it is difficult to remove them from clean rooms. Furthermore, the clean room must include oxygen for operators to work in, and the operators themselves further introduce moisture. Therefore, methods have been explored to reduce the adverse substances. For example, efforts have been made to reduce the interval (Q time) between process stages. Cassettes or front opening unified pods (FOUP) were also periodically cleaned to remove possible adverse substances. However, these methods do not solve the root cause of the problem, and hence can only relieve, but not eliminate, the problem.
Accordingly, new tools and manufacturing methods are needed to prevent the damages caused by moisture, oxygen and AMC sources.